Refresh a lot of the copy

This includes some small and some larger(er) changes, which I'll call out specifically in a moment, but generally:

* Typos and wording (small)
* Bring some tech stuff up to date (small)
* Change a few things about the rails engineering job description (bigger)
@jonathandean and @ndp how's this?  I did leave 4.2 in there to a) try to be amusing and b) indicate that we are well aware of the dreaded .2 Rails update cycle